In recent years images have been recorded by subjecting silver halide photosensitive materials to scanning exposures using laser light.
Laser light sources of various wavelengths (for example argon lasers, helium-neon lasers and semiconductor lasers) have been used in laser scanning exposure apparatus of this type, and appropriate silver halide photosensitive materials have been used in each type of apparatus. That is to say, the emulsion of a silver halide photosensitive material which is suitable for a certain type of laser light source is not always suitable for use with a different laser light source, changes having to be made with respect to the sensitizing dyes, and so the silver halide photosensitive materials which are used in exposing devices which have different laser light sources must generally differ in terms of emulsion design.
Conventionally, this method of recording has been used principally in the printing field, and so the silver halide photographic materials used have, in the main, achieved gradation by means of the size of screening dots, and they have been designed to give the best response when developed in a high contrast development bath. However, more recently, it has become desirable to reproduce continuous tone images, such as images for medical diagnostic purposes for example, using laser scanning exposures.
As an example, silver halide photosensitive materials for use with helium-neon laser light sources in which a coarse grained silver halide emulsion of average grain size from 0.5 to 1.0 .mu.m is mixed with a fine grained silver halide emulsion of average grain size from 0.1 to 0.4. .mu.m, and in which the film is hardened in such a way that the fusion time is greater than a fixed value, have been disclosed in JP-A-59-102229 (The term "JP A" as used herein signifies an "unexamined published Japanese patent application").
However, the silver halide photosensitive materials actually disclosed in JP-A-59-102229 have a disadvantage in that there is strong surface reflection therewith. Thus it is difficult to view the image, and since they have been designed in such a way as to be compatible with the normal processing (90 second processing) used for X ray photosensitive materials, there is a further disadvantage in that they cannot be subjected to rapid development processing (for example, with a time from the commencement of development, through fixing and washing to the completion of drying, within 75 seconds).
Furthermore, the use of a photosensor in which an LED which has a peak emission in the region of 950 nm is combined with a light receiving element is common in the above mentioned laser scanning exposure apparatus for detecting the position of the photosensitive material. However, silver halide photosensitive materials normally have virtually no absorption in the region of 950 nm when the grain size of the emulsion is small and the coated weight of silver is low (which is to say that the material does not have sufficient absorbance to enable the photosensor to detect the presence of the photosensitive material). Consequently, the inclusion of a dye which absorbs at this wavelength in the photosensitive material has been considered so that position detection can be carried out with such an LED. However, if these dyes are not washed out during processing and they are left behind in the photosensitive material they have an adverse effect when viewing the image. This means that an adequate washing process must be carried out in order to eliminate the residual coloration and this in turn means that rapid processing is more difficult to achieve.